The present invention relates generally to spinal fusion methods. In particular aspects, the invention relates to spinal fusion methods employing an osteogenic material delivered to the interbody space along with a barrier material positioned to inhibit migration of the osteogenic material.
As further background, intervertebral discs, located between the endplates of adjacent vertebrae, stabilize the spine, distribute forces between vertebrae, and cushion vertebral bodies. A normal intervertebral disc includes a semi-gelatinous component, the nucleus pulposus, which is surrounded and confined by an outer, fibrous ring called the annulus fibrosus. In a healthy, undamaged spine, the annulus fibrosus prevents the nucleus pulposus from protruding outside the disc space.
Spinal discs may be displaced or damaged due to trauma, disease or aging. Disruption of the annulus fibrosus allows the nucleus pulposus to protrude into the vertebral canal, a condition commonly referred to as a herniated or ruptured disc. The extruded nucleus pulposus may press on a spinal nerve, which may result in nerve damage, pain, numbness, muscle weakness and paralysis. Intervertebral discs may also deteriorate due to the normal aging process or disease. As a disc dehydrates and hardens, the disc space height will be reduced leading to instability of the spine, decreased mobility and pain.
In certain instances, the only relief from the symptoms of these conditions is a discectomy, or surgical removal of a portion or all of an intervertebral disc, followed by fusion (arthrodesis) of the adjacent vertebrae. For these purposes, loadbearing implants are often used to maintain the disc space while new bone growth and arthrodesis are achieved. A variety of such implants have been suggested and/or used, including hollow spinal cages that can be filled with osteogenic material, prior to insertion into the intervertebral space. Apertures defined in the cage communicate with the hollow interior to provide a path for tissue growth between the vertebral endplates. Interbody spinal implants fabricated from bone have also been employed. These include for instance threaded bone dowel products and impacted spacers. An osteogenic substance is typically implanted in conjunction with these spacers to achieve fusion.
Minimally-invasive spinal fusion procedures have been developed, including those involving anterior surgical approaches, e.g. using laproscopic instrumentation, and those involving posterior surgical approaches, e.g. using introducer sleeves. In these approaches, surgical access is provided to the interbody space through the cannulated device (e.g. laproscope or sleeve), and one or more loadbearing implants are introduced through the cannulated device. Oftentimes, the surgeon will pack an osteogenic graft material into an opening or recess in the loadbearing implant prior to introduction and/or in and around the implant, to assist in the fusion process. Access to the surgical field in the interbody space can be somewhat limited, especially in minimally invasive procedures. Nonetheless, techniques for implant and graft placement and retention need to be conducted in a manner that ensures the opportunity for a positive surgical outcome.
In light of this background, there exist needs for improved and/or alternative devices, techniques and systems that are useful for the conduct of interbody spinal fusion procedures. The present invention addresses these needs.